The Role of Dopamine, Reward Learning and Prefrontal Activity in Expectation-induced Mood Enhancement
Status:
Recruiting
Trial end date:
2024-06-30
Target enrollment:
Participant gender:
Summary
Although placebo effects on depressive symptoms are well documented, the underlying
mechanisms and moderating factors of expectation effects on mood and depression are poorly
understood. Various studies show reduced reward processing in clinical and subclinical
depression, presumably due to abnormalities in the dopamine (DA) system. Here, the
investigators will test whether expectation-induced mood enhancement is mediated by
endogenous DA activity and reward learning, and moderated by individual differences in
depression-related personality traits. Healthy participants (N=296) will be tested for
potentially relevant personality traits and given an inactive substance (placebo) or a DA
D2-receptor antagonist sulpiride (400 mg) in combination with a low vs. high expectation
manipulation (fully crossed 2x2 placebo design) before performing a probabilistic
reinforcement learning task, an effort expenditure task, and undergo a depressed mood
induction procedure. Further, EEG indices will be assessed throughout the tasks.
The investigators expect that positive expectation improves participants' reinforcement
learning, increases participants' willingness to make effort in order to obtain reward, and
leads to less depressive symptoms as indicated by mood ratings upon depressive mood
induction. If the overall effect of positive expectations is mediated by DA, high-dose
sulpiride should block expectation-induced effects, i.e., the anticipated enhanced
reinforcement learning and effort expenditure as well as mood improvement in the high vs. low
expectation group.